Nitrogen containing polymers as levelers

ABSTRACT

Polymers of reaction products of polyamines and nitrogen containing cyclic compounds are included in metal electroplating compositions to provide level metal deposits on substrates.

FIELD OF THE INVENTION

The present invention is directed to nitrogen containing polymers aslevelers for electroplating compositions. More specifically, the presentinvention is directed to nitrogen containing polymers as levelers forelectroplating compositions which are reaction products of polyaminesand nitrogen containing cyclic compounds with good thermal reliabilityand throwing power.

BACKGROUND OF THE INVENTION

Methods for electroplating articles with metal coatings generallyinvolve passing a current between two electrodes in a plating solutionwhere one of the electrodes is the article to be plated. A typical acidcopper plating solution comprises dissolved copper, usually coppersulfate, an acid electrolyte such as sulfuric acid in an amountsufficient to impart conductivity to the bath, and proprietary additivesto improve the uniformity of the plating and the quality of the metaldeposit. Such additives include accelerators, levelers, and suppressors,among others.

Electrolytic copper plating solutions are used in a variety ofindustrial applications, such as decorative and anticorrosion coatings,as well as in the electronics industry, particularly for the fabricationof printed circuit boards and semiconductors. For circuit boardfabrication, copper is electroplated over selected portions of thesurface of a printed circuit board, into blind vias and onto the wallsof through-holes passing between the surfaces of the circuit board basematerial. The walls of a through-hole are first made conductive, such asby electroless metal deposition, before copper is electroplated onto thewalls of the through-hole. Plated through-holes provide a conductivepathway from one board surface to the other. For semiconductorfabrication, copper is electroplated over a surface of a wafercontaining a variety of features such as vias, trenches or combinationsthereof. The vias and trenches are metallized to provide conductivitybetween various layers of the semiconductor device.

It is well known in certain areas of plating, such as in electroplatingof printed circuit boards (“PCBs”), that the use of accelerators and/orlevelers in the electroplating bath can be crucial in achieving auniform metal deposit on a substrate surface. Plating a substrate havingirregular topography can pose particular difficulties. Duringelectroplating a voltage drop variation typically exists along anirregular surface which can result in an uneven metal deposit. Platingirregularities are exacerbated where the voltage drop variation isrelatively extreme, that is, where the surface irregularity issubstantial. As a result, a thicker metal deposit, termed overplating,is observed over such surface irregularities. Consequently, a metallayer of substantially uniform thickness is frequently a challengingstep in the manufacture of electronic devices. Leveling agents are oftenused in copper plating baths to provide substantially uniform, or level,copper layers in electronic devices.

The trend of portability combined with increased functionality ofelectronic devices has driven the miniaturization of PCBs. Conventionalmultilayer PCBs with through-hole interconnect vias are not always apractical solution. Alternative approaches for high densityinterconnects have been developed, such as sequential build uptechnologies, which utilize blind vias. One of the objectives inprocesses that use blind vias is the maximizing of via filling whileminimizing thickness variation in the copper deposit across thesubstrate surface. This is particularly challenging when the PCBcontains both through-holes and blind vias.

Generally, leveling agents used in copper plating baths provide betterleveling of the deposit across the substrate surface but tend tocompromise the throwing power of the electroplating bath. Throwing poweris defined as the ratio of the hole center copper deposit thickness toits thickness at the surface. Newer PCBs are being manufactured thatcontain both through-holes and blind vias. Current bath additives, inparticular current leveling agents, do not provide level copper depositson the substrate surface and fill through-holes and/or fill blind viaseffectively. Accordingly, there remains a need in the art for levelingagents for use in copper electroplating baths used in the manufacture ofPCBs that provide level copper deposits while not significantlyaffecting the throwing power of the bath.

SUMMARY OF THE INVENTION

Polymers include a reaction product of one or more polyamines with oneor more nitrogen containing compounds having formula:

where A is a substituted or unsubstituted 5-6 membered aromaticheterocyclic ring, a substituted or unsubstituted 5-6 membered aromaticcarbocyclic ring or a substituted or unsubstituted fused heterocyclicring system of a five membered heterocyclic ring to a six memberedcarbocyclic or heterocyclic ring, R is a covalent bond, linear orbranched (C₁-C₁₂)alkyl, —NH—, —R₂NH— or —R₂NHR₃— joining the carbon atomor heteroatom of ring A or an atom of a substituent group on ring A to—C(O)—O—R₁, n is an integer of 2 or greater, R₂ and R₃ are the same ordifferent and are linear or branched (C₁-C₁₂)alkyl, and with the provisothat there is at least one nitrogen atom in ring A, in a substituent ofring A or in R, and R₁ is hydrogen or linear or branched (C₁-C₁₂)alkyl,optionally, formula (I) may be positively charged.

Metal electroplating compositions include: one or more sources of metalions, an electrolyte, and one or more polymers, the one or more polymersinclude a reaction product of one or more polyamines and one or morenitrogen containing compounds having formula:

where A is a substituted or unsubstituted 5-6 membered aromaticheterocyclic ring, a substituted or unsubstituted 5-6 membered aromaticcarbocyclic ring or a substituted or unsubstituted fused heterocyclicring system of a five membered heterocyclic ring to a six memberedcarbocyclic or heterocyclic ring, R is a covalent bond, linear orbranched (C₁-C₁₂)alkyl, —NH—, —R₂NH— or —R₂NHR₃— joining the carbon atomor heteroatom of ring A to the —C(O)—O—R₁, n is an integer of 2 andgreater, R₂ and R₃ are the same or different and are linear or branched(C₁-C₁₂)alkyl, and with the proviso that there is at least one nitrogenatom in ring A, in a substituent on ring A or in R, and R₁ is hydrogenor linear or branched (C₁-C₁₂)alkyl, optionally, formula (I) may bepositively charged.

Methods include contacting a substrate to be metal plated with a metalelectroplating composition including: a source of metal ions, anelectrolyte, and one or more polymers, the one or more polymers includea reaction product of one or more polyamines and one or more nitrogencontaining compounds having formula:

where A is a substituted or unsubstituted 5-6 membered aromaticheterocyclic ring, a substituted or unsubstituted 5-6 membered aromaticcarbocyclic ring or a substituted or unsubstituted fused heterocyclicring system of a five membered heterocyclic ring to a six memberedcarbocyclic or heterocyclic ring, R is a covalent bond, linear orbranched (C₁-C₁₂)alkyl, —NH—, —R₂NH— or —R₂NHR₃— joining the carbon atomor heteroatom of ring A or an atom of a substituent on ring A to—C(O)—O—R₁, n is an integer of 2 or greater, R₂ and R₃ are the same ordifferent and are linear or branched (C₁-C₁₂)alkyl, and with the provisothat there is at least one nitrogen atom in ring A, in a substituent ofring A or in R, and R₁ is hydrogen or linear or branched (C₁-C₁₂)alkyl,optionally, formula (I) may be positively charged; applying a current;and depositing the metal on the substrate.

The polymers provide metal layers having a substantially level surfaceacross a substrate, even on substrates having small features and onsubstrates having a variety of feature sizes. The metal layers depositedaccording to the methods have improved thermal stability as compared tometal deposits from electroplating baths using conventional levelingagents. Further, the methods effectively deposit metals in through-holesand blind via holes such that the metal plating compositions have goodthrowing power.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification the following abbreviations shallhave the following meanings unless the context clearly indicatesotherwise: A=amperes; A/dm²=amperes per square decimeter; ° C.=degreesCentigrade; g=gram; mg=milligram; ppm=parts per million;mmol=millimoles; L=liter, L/m=liters per minute; μm=micron=micrometer;mm=millimeters; cm=centimeters; DI=deionized; mL=milliliter; Mw=weightaverage molecular weight; and Mn=number average molecular weight; andv/v=volume to volume. All amounts are percent by weight unless otherwisenoted. All numerical ranges are inclusive and combinable in any order,except where it is clear that such numerical ranges are constrained toadd up to 100%.

As used throughout the specification, “feature” refers to the geometrieson a substrate. “Apertures” refer to recessed features includingthrough-holes and blind vias. As used throughout this specification, theterm “plating” refers to metal electroplating. “Deposition” and“plating” are used interchangeably throughout this specification.“Halide” refers to fluoride, chloride, bromide and iodide. “Accelerator”refers to an organic additive that increases the plating rate of theelectroplating bath. A “suppressor” refers to an organic additive thatsuppresses the plating rate of a metal during electroplating. “Leveler”refers to an organic compound that is capable of providing asubstantially level or planar metal layer. The terms “leveler” and“leveling agent” are used interchangeably throughout this specification.The terms “printed circuit boards” and “printed wiring boards” are usedinterchangeably throughout this specification. The articles “a” and “an”refer to the singular and the plural.

The polymers are reaction products of one or more polyamines and one ormore nitrogen containing compounds having formula:

where A is a substituted or unsubstituted 5-6 membered aromaticheterocyclic ring, a substituted or unsubstituted 5-6 membered aromaticcarbocyclic ring or a substituted or unsubstituted fused heterocyclicring system of a five membered heterocyclic ring to a six memberedcarbocyclic or heterocyclic ring, R is a covalent bond, linear orbranched (C₁-C₁₂)alkyl, —NH—, —R₂NH— or —R₂NHR₃—, preferably R is alinear or branched (C₁-C₁₂)alkyl, joining —C(O)—O—R₁ to a carbon atom orhetero atom of ring A or to an atom of a substituent group joined toring A, more preferably R is a linear or branched (C₁-C₁₂)alkyl joining—C(O)—O—R₁ to a nitrogen atom of ring A, n is an integer of 2 orgreater, preferably 2 to 4, more preferably n is 2, R₂ and R₃ are thesame or different and are linear or branched (C₁-C₁₂)alkyl, and with theproviso that there is at least one nitrogen atom in either ring A, in asubstituent on ring A, or in R, and R₁ is hydrogen or linear or branched(C₁-C₁₂)alkyl. Hetero atoms in the heterocyclic aromatic rings includeone or more of nitrogen, sulfur and oxygen. Preferably, the hetero atomis nitrogen. Substituent groups include, but are not limited to linearor branched alkyl; hydroxyl; amino; amide; linear or branchedhydroxyalkyl; halide, linear or branched haloalkyl; thio; linear orbranched thioalkyl; linear or branched alkoxy; primary, secondary ortertiary amine; carboxyl, linear or branched carboxyalkyl; aldehyde;ketone; and substituted or unsubstituted aryl. Substituent groups on thearyl may include the recited foregoing groups. Formula (I) may bepositively charged.

Compounds of five and six membered aromatic carbocyclic rings include,but are not limit to the following:

where R₅, R₆, R₇, R₈, R₉ and R₁₀ may be the same or different and may behydrogen, hydroxyl, amino; amide; linear or branchedhydroxy(C₁-C₁₀)alkyl, linear or branched (C₁-C₁₀)alkoxy, halide, linearor branched (C₁-C₁₀)alkyl halide, —NH₂, primary, secondary or tertiarylinear or branched (C₁-C₁₂)alkyl amine, aldehyde, ketone, carboxyl,linear or branched carboxy(C₁-C₁₀)alkyl, linear or branched(C₁-C₂₀)alkyl; a substituted or unsubstituted aryl; or substituted orunsubstituted alkylaryl. The atoms of an adjacent pair of R₅-R₁₀, suchas the carbon atoms of R₈ and R₉ of formula (II) or formula (III) may betaken together to form an unsaturated five or six membered substitutedor unsubstituted ring. Preferably, at least one of R₅ to R₁₀ is —NH₂ ora primary or secondary amine. When A is a carbocyclic ring, preferably,the carbocyclic ring is a six membered ring. Exemplary compounds havethe following general formula:

where R₆ to R₁₀ are as defined above and R′ is a linear or branched(C₁-C₁₂)alkyl.

Compounds of five and six membered aromatic heterocyclic rings include,but are not limit to the following:

where variables t, u, v, w, y and z are independently carbon, nitrogen,oxygen or sulfur with the proviso that at least one of the variables iscarbon and at least one is nitrogen, preferably, the hetero atoms areall nitrogen; a is an integer of 1 to 5, preferably from 1 to 4, b is aninteger of 1 to 6, preferably from 1 to 5, and R₁₁ may be the same ordifferent and include, but is not limited to hydrogen, hydroxyl, amino;amide; linear or branched hydroxy(C₁-C₁₀)alkyl, linear or branched(C₁-C₁₀)alkoxy, halide, linear or branched (C₁-C₁₀)alkyl halide, —NH₂,primary, secondary or tertiary linear or branched (C₁-C₁₂)alkyl amine,aldehyde, ketone, carboxyl, linear or branched carboxy(C₁-C₁₀)alkyl,linear or branched (C₁-C₂₀)alkyl, thio, thioalkyl, a substituted orunsubstituted aryl; or a substituted or unsubstituted alkylaryl. Anadjacent pair of atoms of R₁₁ groups of structures (VI) or (VII) may betaken together to form an unsaturated six membered substituted orunsubstituted ring fused to ring structures (VI) or an unsaturated fivemembered substituted or unsubstituted ring fused to rings structure(VII) having formula (VIII).

where t, u, v, w, y and z and R₁₁ are defined as above and c is aninteger of 1 to 4 and d is an integer of 1 to 3. Preferably, R₁₁ is oneor more of hydrogen, hydroxyl, —NH₂, primary or secondary amine andlinear or branched (C₁-C₁₀)alkyl, more preferably, R₁₁ is one or more ofhydrogen, hydroxyl and linear or branched (C₁-C₁₀)alkyl. Representativesof such compounds are imidazoles, triazoles, tetrazoles, thiazoles,benzimidazoles, oxazoles, aminopyridines, alkylaminopyridines andderivatives thereof. Preferably the nitrogen compounds are five memberedheterocyclic rings as formula (VI) above where the hetero atoms of thefive membered heterocyclic ring are nitrogen. Exemplary compoundsinclude the following:

where R₁₂, R₁₃, R₁₄, R₁₅, R₁₆ and R₁₇ are the same or different andinclude, but are not limited to hydrogen, linear or branched(C₁-C₁₂)alkyl, substituted or unsubstituted aryl, hydroxylalkyl,hydroxyl, thio, thioalkyl, —NH₂, primary amine or secondary amine, wherem is an integer of 0 to ten with the proviso that when m is 0 nitrogenis covalently bonded to the carbon of the ring.

The carbocyclic and heterocyclic nitrogen containing compounds describedabove are reacted with compounds having general formula:

X—R—C(O)—O—R₁   (X)

where R and R₁ are as defined above and X is a halide such as chloride,fluoride, bromide and iodide. Preferably the halide is chloride,fluoride or bromide. More preferably the halide is chloride or fluoride.The reaction takes place in the presence of tetrahydrofuran (THF) andsodium hydride under chilled conditions of 0° C. to 4° C. and stirringto provide products having the formula (I).

Exemplary aromatic nitrogen containing compounds have the followinggeneral formula:

wherein R, R₁, R₁₂, R₁₆, X, the variable m and the variable u are asdefined above where preferably the variable u is carbon or nitrogen, R₁₈is the same as R₁₁ and f is an integer 0 to 2, preferably 1 or 2, and R″is a linear or branched (C₁-C₁₂)alkyl or (C₁-C₁₂)ether.

Polyamines include, but are not limited to, compounds having generalformula:

where R₂₁ is a —(CH₂—CH₂)_(p)—,—(CH₂—CH₂)_(p)—(NH—R₂₄—NH)_(q)—(CH₂—CH₂)_(p)—,—(CH₂—CH₂)_(p)—(O—R₂₅—O)_(r)—(CH₂)_(p)—, a substituted or unsubstituted(C₆-C₁₈)aryl, where R₂₄ is —(CH₂—CH₂)_(p)—, or

where p, q and r are independently integers of one or greater,preferably from 1 to 10; R₂₂ and R₂₃ are independently hydrogen, linearor branched (C₁-C₁₂)alkyl or substituted or unsubstituted (C₆-C₁₈)aryl,where when R₂₂ and R₂₃ are (C₁-C₁₂)alkyl, they may be taken togetherwith all of the atoms in the group to form a ring. R₂₅ is linear orbranched (C₂-C₁₀)alkyl. Substituents on the aryl groups include, but arenot limited to linear or branched (C₁-C₁₂)alkyl, linear or branchedhydroxy(C₁-C₁₂)alkyl, or hydroxyl.

One or more compounds of formula (I) are reacted with one or morecompounds of formula (XIIa) and (XIIb) in an organic solvent andrefluxing at temperatures of 45° C. to 50° C. under an inert gasatmosphere. Typically, refluxing is done under a nitrogen atmosphere.Alternatively, the compounds of formula (I) and one or more compounds offormula (XIIa) and (XIIb) may be cooked with or without solvent. Themolar reaction ratio of the compounds of formula (I) to the one or morecompounds of formula (XIIa) and (XIIb) may range from 1:0.1 to 1:2,preferably from 0.8:1 to 1:0.8. The compounds of formula (I) are joinedto the compounds of formula (XIIa) and (XIIb) by an amide linkage. Suchpolymers have a general formula:

where R, R₂₁, R₂₂ and R₂₃ are as defined above and g is an integer of 2or greater, optionally, formula (XIII) may have a positive charge.Examples of such polymers with the amide linkage are the following:

where R, R₁₂ R₁₃, R₁₄, X⁻, p, u and g are defined above.

The plating composition and method are useful in providing asubstantially level plated metal layer on a substrate, such as a printedcircuit board. Also, the plating composition and method are useful infilling apertures in a substrate with metal. Also, the metal depositsare substantially crack-free and have good throwing power.

Any substrate upon which metal can be electroplated is useful in thepresent invention. Such substrates include, but are not limited toprinted wiring boards, integrated circuits, semiconductor packages, leadframes and interconnects. An integrated circuit substrate may be a waferused in a dual damascene manufacturing process. Such substratestypically contain a number of features, particularly apertures, having avariety of sizes. Through-holes in a PCB may have a variety ofdiameters, such as from 50 μm to 350 μm in diameter. Such through-holesmay vary in depth, such as from 35 μm to 100 μm. PCBs may contain blindvias having a wide variety of sizes, such as up to 200 μm, or greater.

Conventional metal plating compositions may be used. The metal platingcompositions contain a source of metal ions, an electrolyte, and aleveling agent, where the leveling agent is a reaction product of one ormore nitrogen-containing compounds of formula (I) with one or morepolyamine compounds. The metal plating compositions may contain a sourceof halide ions, an accelerator and a suppressor. Metals which may beelectroplated from the compositions include, but are not limited to,copper, tin and tin/copper alloys.

Suitable copper ion sources are copper salts and include withoutlimitation: copper sulfate; copper halides such as copper chloride;copper acetate; copper nitrate; copper fluoroborate; copperalkylsulfonates; copper arylsulfonates; copper sulfamate; and coppergluconate. Exemplary copper alkylsulfonates include copper(C₁-C₆)alkylsulfonate and more preferably copper (C₁-C₃)alkylsulfonate.Preferred copper alkylsulfonates are copper methanesulfonate, copperethanesulfonate and copper propanesulfonate. Exemplary copperarylsulfonates include, without limitation, copper phenyl sulfonate,copper phenol sulfonate and copper p-toluene sulfonate. Mixtures ofcopper ion sources may be used. One or more salts of metal ions otherthan copper ions may be added to the present electroplating baths.Typically, the copper salt is present in an amount sufficient to providean amount of copper metal of 10 to 180 g/L of plating solution.

Suitable tin compounds include, but are not limited to salts, such astin halides, tin sulfates, tin alkane sulfonate such as tin methanesulfonate, tin aryl sulfonate such as tin phenyl sulfonate, tin phenolsulfonate and tin toluene sulfonate, tin alkanol sulfonate. The amountof tin compound in these electrolyte compositions is typically an amountthat provides a tin content in the range of 5 to 150 g/L. Mixtures oftin compounds may be used in an amount as described above.

The electrolyte useful in the present invention may be alkaline oracidic. Typically the electrolyte is acidic. Suitable acidicelectrolytes include, but are not limited to, sulfuric acid, aceticacid, fluoroboric acid, alkanesulfonic acids such as methanesulfonicacid, ethanesulfonic acid, propanesulfonic acid and trifluoromethanesulfonic acid, arylsulfonic acids such as phenyl sulfonic acid, phenolsulfonic acid and toluene sulfonic acid, sulfamic acid, hydrochloricacid, and phosphoric acid. Mixtures of acids may be advantageously usedin the present metal plating baths. Preferred acids include sulfuricacid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid,and mixtures thereof. The acids may be present in an amount in the rangeof from 1 to 300 g/L. Electrolytes are generally commercially availablefrom a variety of sources and may be used without further purification.

Such electrolytes may optionally contain a source of halide ions.Typically chloride ions are used. Exemplary chloride ion sources includecopper chloride, tin chloride and hydrochloric acid. A wide range ofhalide ion concentrations may be used in the present invention.Typically, the halide ion concentration is in the range of from 0 to 100ppm based on the plating bath. Such halide ion sources are generallycommercially available and may be used without further purification.

The plating compositions typically contain an accelerator. Anyaccelerators (also referred to as brightening agents) are suitable foruse in the present invention. Such accelerators are well-known to thoseskilled in the art. Accelerators include, but are not limited to,N,N-dimethyl-dithiocarbamic acid-(3-sulfopropyl)ester;3-mercapto-propylsulfonic acid-(3-sulfopropyl)ester;3-mercapto-propylsulfonic acid sodium salt; carbonicacid-dithio-o-ethylester-s-ester with 3-mercapto-1-propane sulfonic acidpotassium salt; bis-sulfopropyl disulfide;3-(benzothiazolyl-s-thio)propyl sulfonic acid sodium salt; pyridiniumpropyl sulfobetaine; 1-sodium-3-mercaptopropane-1-sulfonate;N,N-dimethyl-dithiocarbamic acid-(3-sulfoethyl)ester; 3-mercapto-ethylpropylsulfonic acid-(3-sulfoethyl)ester; 3-mercapto-ethylsulfonic acidsodium salt; carbonic acid-dithio-o-ethylester-s-ester with3-mercapto-1-ethane sulfonic acid potassium salt; bis-sulfoethyldisulfide; 3-(benzothiazolyl-s-thio)ethyl sulfonic acid sodium salt;pyridinium ethyl sulfobetaine; and1-sodium-3-mercaptoethane-1-sulfonate. Accelerators may be used in avariety of amounts. In general, accelerators are used in an amount of0.1 ppm to 1000 ppm.

Any compound capable of suppressing the metal plating rate may be usedas a suppressor in the present electroplating compositions. Suitablesuppressors include, but are not limited to, polypropylene glycolcopolymers and polyethylene glycol copolymers, including ethyleneoxide-propylene oxide (“EO/PO”) copolymers and butyl alcohol-ethyleneoxide-propylene oxide copolymers. Suitable butyl alcohol-ethyleneoxide-propylene oxide copolymers are those having a weight averagemolecular weight of 100 to 100,000, preferably 500 to 10,000. When suchsuppressors are used, they are typically present in an amount in therange of from 1 to 10,000 ppm based on the weight of the composition,and more typically from 5 to 10,000 ppm.

In general, the reaction products of the compounds of formula (I) andone or more polyamine have a number average molecular weight (Mn) of 500to 10,000, typically from 1000 to 50,000, preferably from 2000 to 8000,although reaction products having other Mn values may be used. Suchreaction products may have a weight average molecular weight (Mw) valuein the range of 1000 to 50,000, typically from 5000 to 30,000, althoughother Mw values may be used.

The amount of the reaction product (leveling agent) used in the metalelectroplating compositions depend upon the particular leveling agentsselected, the concentration of the metal ions in the electroplatingcomposition, the particular electrolyte used, the concentration of theelectrolyte and the current density applied. In general, the totalamount of the leveling agent in the electroplating composition is from0.01 ppm to 5,000 ppm based on the total weight of the platingcomposition, although greater or lesser amounts may be used. Preferably,the total amount of the leveling agent is from 0.1 to 1000 ppm, morepreferably from 0.1 to 500 ppm.

The electroplating compositions may be prepared by combining thecomponents in any order. It is preferred that the inorganic componentssuch as source of metal ions, water, electrolyte and optional halide ionsource are first added to the bath vessel followed by the organiccomponents such as leveling agent, accelerator, suppressor, and anyother organic component.

The electroplating compositions may optionally contain a second levelingagent. Such second leveling agent may be another leveling agent of thepresent invention, or alternatively, may be any conventional levelingagent. Suitable conventional leveling agents that can be used incombination with the present leveling agents include, withoutlimitations, those disclosed in U.S. Pat. No. 6,610,192 to Step et al.,U.S. Pat. No. 7,128,822 to Wang et al., U.S. Pat. No. 7,374,652 toHayashi et al. and U.S. Pat. No. 6,800,188 to Hagiwara et al. Suchcombination of leveling agents may be used to tailor the characteristicsof the plating bath, including leveling ability and throwing power.

Typically, the plating compositions may be used at any temperature from10 to 65° C. or higher. Preferably, the temperature of the platingcomposition is from 10 to 35° C. and more preferably from 15 to 30° C.

In general, the metal electroplating compositions are agitated duringuse. Any suitable agitation method may be used and such methods arewell-known in the art. Suitable agitation methods include, but are notlimited to air sparging, work piece agitation, and impingement.

Typically, a substrate is electroplated by contacting the substrate withthe plating composition. The substrate typically functions as thecathode. The plating composition contains an anode, which may be solubleor insoluble. Potential is typically applied to the cathode. Sufficientcurrent density is applied and plating performed for a period of timesufficient to deposit a metal layer having a desired thickness on thesubstrate as well as fill blind vias and/or through-holes. Currentdensities, include, but are not limited to, the range of 0.05 to 10A/dm², although higher and lower current densities may be used. Thespecific current density depends in part upon the substrate to be platedand the leveling agent selected. Such current density choice is withinthe abilities of those skilled in the art.

An advantage of the present invention is that substantially level metaldeposits are obtained on a PCB. By “substantially level” metal layer ismeant that the step height, i.e., the difference between areas of densevery small apertures and areas free of or substantially free ofapertures, is less than 5 μm, and preferably less than 1 μm.Through-holes and/or blind vias in the PCB are substantially filled. Afurther advantage of the present invention is that a wide range ofapertures and aperture sizes may be filled.

Throwing power is defined as the ratio of the average thickness of themetal plated in the center of a through-hole compared to the averagethickness of the metal plated at the surface of the PCB sample and isreported as a percentage. The higher the throwing power, the better theplating composition is able to fill the through-hole. Metal platingcompositions of the present invention have a throwing power of ≧65%,preferably ≧70%. Metal plating compositions of the present inventionalso show improved thermal stability of a metal plated substrate ascompared to many conventional metal plating compositions.

While the methods of the present invention have been generally describedwith reference to printed circuit board manufacture, it is appreciatedthat the present invention may be useful in any electrolytic processwhere an essentially level or planar metal deposit and filled aperturesare desired. Such processes include semiconductor packaging andinterconnect manufacture.

The following examples are intended to further illustrate the inventionbut are not intended to limit its scope.

EXAMPLE 1

6.8 g (100 mmols) of imidazole and 2.4 g (100 mmols) of sodium hydridewere dissolved in 50 ml of anhydrous THF. The mixture was stirred andcooled in an ice bath for 2 hours until the formation of hydrogen gasceased. 21.6 g (200 mmols) of ethyl chloroacetate was added and themixture was refluxed for 12 hours. After removing the solvent byevaporation, the remaining residue was extracted by acetonitrile toobtain 1H-imidazolium 1,3-bis(2-methoxy-2-oxoethyl). The end product wasconfirmed by NMR spectrum. The NMR spectra were recorded at 25° C. usinga Bruker 400 MHz spectrometer operating at 400.13 MHz for 1H NMR.

To a three necked flask 4 g (15.3 mmols) of 1H-imidazolium1,3-bis(2-methoxy-2-oxoethyl), 1.7 g (15.3 mmols) ofhexamethylenediamine and 20 ml of acetonitrile were added. The mixturewas refluxed for 48 hours in an inert N₂ atmosphere. The final product(product 1) precipitated out during the reaction. The final product wasconfirmed by NMR spectrum which had the peaks δ ppm: 8.82-8.88 (s, 1H,H_(aram)); 7.65-7.52 (m, 2H, H_(aram)); 4.89-4.75 (m, 4H, 2× CH₂—N),3.31 (broad s, 4H, 2× CH₂—NH); 1.60 (broad s, 4H, 2× CH₂—NH); and 1.40(broad s, 4H, 2× CH₂—CH₂—CH₂—NH) and had the following formula:

The variable g is defined above. The molecular weight of the end productwas then determined by Agilent 1200 GPC unit equipped with IR detector,a PL Aquagel-OH 30 8 μm 300×7.5 mm size exclusion separation column anda PL Aquagel-OH 8 μm 50×7 5 mm guard column. The column temperature was30° C. The mobile phase was performed in 0.1% v/v trifluoroacetic acidin DI water at a flow rate of 1 mL/min GPC calibrations were performedusing polyethylene glycol standards. The Mn was determined to be 3,458and the Mw was determined to be 7,504.

EXAMPLE 2

8.2 g (100 mmols) of 4-methyl imidazole and 2.4 g (100 mmols) of sodiumhydride were dissolved in 50 ml of anhydrous THF. The mixture wasstirred and cooled in an ice bath for 2 hours until the formation ofhydrogen gas ceased. 21.6 g (200 mmols) of ethyl chloroacetate was thenadded to the mixture. After refluxing for 12 hours the solvent wasremoved by evaporation and the remaining residue was extracted byacetonitirile to obtain 1H-imidazolium 1,3-bis(2-methoxy-2-oxoethyl).The end product was confirmed by NMR spectrum.

To a three necked flask 4.2 g (15.3 mmols) of 1H-4-methyl imidazolium1,3-bis(2-methoxy-2-oxoethyl), 1.7 g (15.3 mmols) ofhexamethylenediamine and 20 ml of acetonitrile were added. The mixturewas refluxed for 48 hours under an inert N₂ atmosphere. The finalproduct (product 2) precipitated out during the reaction. The productwas confirmed as having the same general formula as XIII by NMRspectrum. The molecular weight of the final product was determined to beMn=1,367 and Mw=2,708 by Agilent 1200 GPC.

Four copper electroplating solutions were prepared and each was added toseparate Haring Cells. Two of the copper electroplating solutions had 2ppm of accelerator and the other two had 3 ppm of accelerator. Theformulation of the copper electroplating solutions had the formulationin Table 1 below:

TABLE 1 COMPONENT AMOUNT Copper sulfate pentahydrate 73 g/L Sulfuricacid 235 g/L Chloride ion as HCL 60 ppm EO/PO copolymer with terminalhydroxyl 1.5 g/L groups and molecular weight <5000 (suppressor)Disulfide compound with sulfonic acid groups 2 to 3 ppm and molecularweight <1000 (accelerator)

Product 1 was added to two of the Haring Cells in amounts of 10 ppm and20 ppm. Product 2 was added to the other two Haring Cells in amounts of0.5 ppm and 1 ppm. A cleaned copper test panel was placed in each HaringCell. The test panels were 3 2 mm thick double-sided FR4 PCBs 5 cm×9.5cm with a plurality of through-holes having diameters of 300 μm.

The test panels functioned as cathodes. The counter electrode was aconventional soluble copper electrode. The electrodes were connected toa rectifier and a current density of 2.2 A/dm² was applied in eachHaring Cell for 80 minutes. The temperature of each solution was 25° C.during electroplating.

After copper electroplating the test panels were removed from the HaringCells and rinsed with de-ionized water for one minute. They were thenplaced in a solution of ANTI-TARNISH™ 7130 solution (available from theDow Chemical Company, Midland, Mich.) for one minute. The panels wereagain rinsed with de-ionized water for one minute and dried withcompressed air. The copper deposit on each panel appeared bright anduniform to the naked eye.

The area of the panel with the through-holes was cut, mounted andcross-sectioned. The thickness of the copper deposit was measured on thesurface of each panel as well as the average thickness in thethrough-holes using optical microscopy. Measured thicknesses wereadjusted for through-hole location diameter after cross-sectioning.Throwing power was calculated by determining the ratio of the averagethickness of the metal plated in the center of the through-hole comparedto the average thickness of the metal plated at the surface of the PCBsample. The results are in Table 2 as a percentage.

The percent cracking was determined according to the industry standardprocedure IPC-TM-650-2.6.8 Thermal Stress, Plated-through Holes,published by IPC (Northbrook, Ill., U.S.A., May 2004, revision E.

TABLE 2 Accel- Hole Surface Reaction Leveler erator thickness thickness% product (ppm) (ppm) (μm) (μm) TP % Cracking 1 10 3 19.0 27.8 68.3 0 120 3 20.2 29.6 68.2 0 2 0.5 2 19.9 28.6 69.6 0 2 1 2 20.2 27.9 72.4 0

The percent cracking for each panel was determined to be 0. Accordingly,no significant cracking occurred on any of the panels.

What is claimed is:
 1. A polymer comprising a reaction product comprising one or more polyamines and one or more nitrogen containing compounds having formula:

wherein A is a substituted or unsubstituted 5-6 membered aromatic heterocyclic ring, a substituted or unsubstituted 5-6 membered aromatic carbocyclic ring or a substituted or unsubstituted fused heterocyclic ring system of a five membered heterocyclic ring to a six membered carbocyclic or heterocyclic ring, R is a covalent bond, linear or branched (C₁-C₁₂)alkyl, —NH—, —R₂NH— or —R₂NHR₃— joining the carbon atom or heteroatom of ring A or an atom of a substituent group on ring A to the —C(O)—O—R₁, n is an integer of 2 or greater, R₂ and R₃ are the same or different and are linear or branched (C₁-C₁₂)alkyl, and with the proviso that there is at least one nitrogen atom in either ring A, a substituent group on ring A or in R, and R₁ is hydrogen or linear or branched (C₁-C₁₂)alkyl, optionally the nitrogen compounds have a net positive charge.
 2. A metal electroplating composition comprises: one or more sources of metal ions, an electrolyte, and one or more polymers, the polymers comprise a reaction product of one or more polyamines and one or more nitrogen containing compounds having formula:

wherein A is a substituted or unsubstituted 5-6 membered aromatic heterocyclic ring, a substituted or unsubstituted 5-6 membered aromatic carbocyclic ring or a substituted or unsubstituted fused heterocyclic ring system of a five membered heterocyclic ring to a six membered carbocyclic or heterocyclic ring, R is a covalent bond, linear or branched (C₁-C₁₂)alkyl, —NH—, —R₂NH— or —R₂NHR₃— joining the carbon atom or heteroatom of ring A or an atom of a substituent group on ring A to the —C(O)—O—R₁, n is an integer of 2 or greater, R₂ and R₃ are the same or different and are linear or branched (C₁-C₁₂)alkyl, and with the proviso that their is at least one nitrogen atom in ring A, a substituent group on ring A or in R, and R₁ is hydrogen or linear or branched (C₁-C₁₂)alkyl, optionally the nitrogen compounds have a net positive charge.
 3. The metal electroplating composition of claim 2, wherein the one or more polymers are included in the composition in amounts from 0.01 ppm to 5,000 ppm.
 4. The metal electroplating composition of claim 2, wherein the one or more sources of metal ions are chosen from copper and tin salts.
 5. The metal electroplating bath of claim 2, further comprising one or more accelerators and suppressors.
 6. A method comprising: a) contacting a substrate to be plated with a metal electroplating composition comprising: one or more sources of metal ions, an electrolyte, and one or more polymers, the one or more polymers comprise a reaction product of one or more polyamines and one or more nitrogen containing compounds having formula:

wherein A is a substituted or unsubstituted 5-6 membered aromatic heterocyclic ring, a substituted or unsubstituted 5-6 membered aromatic carbocyclic ring or a substituted or unsubstituted fused heterocyclic ring system of a five membered heterocyclic ring to a six membered carbocyclic or heterocyclic ring, R is a covalent bond, linear or branched (C₁-C₁₂)alkyl, —NH—, —R₂NH— or —R₂NHR₃— joining the carbon atom or heteroatom of ring A or an atom of a substituent group on ring A to the —C(O)—O—R₁, n is an integer of 2 or greater, R₂ and R₃ are the same or different and are linear or branched (C₁-C₁₂)alkyl, and with the proviso that their is at least one nitrogen atom in ring A, a substituent group or ring A or in R, and R₁ is hydrogen or linear or branched (C₁-C₁₂)alkyl, optionally the nitrogen compounds have a net positive charge; b) applying a current; and c) depositing a metal on the substrate.
 7. The method of claim 6, wherein the one or more sources or metal ions are chosen from copper salts and tin salts.
 8. The method of claim 6 wherein the substrate is a printed circuit board. 